Funded PhD position (M/F), cell mechanics, LadHyX, École Polytechnique

Job Description

Thesis Subject

Mechanical Characterization of cells: from Viscoelasticity to Membrane Rupture

Project Overview
Ultrasound-mediated drug delivery using microbubbles is a promising therapeutic strategy, but its physical principles remain poorly understood. When oscillating near a cell, cavitating microbubbles exert mechanical stresses that can transiently open pores in the plasma membrane, enabling intracellular delivery of therapeutic agents. Yet the biophysical mechanisms governing membrane rupture and how cell mechanical properties determine rupture thresholds are largely unknown. This PhD project, part of an ANR-funded initiative, addresses this gap by combining advanced micropipette-based techniques [1-4] with quantitative mechanical models to dissect cell viscoelastic properties and membrane rupture behavior under controlled stress. The experimental data generated will directly inform computational models and guide optimization of clinical treatment parameters.

Objectives and Methods
During this interdisciplinary thesis with a strong experimental component, we will use micropipette-based techniques to systematically characterize cell mechanical properties and membrane failure behavior under controlled stress. We will work in close collaboration with computational mechanics groups to confront experimental results with continuum models of cell deformation and membrane failure.
The aims of the project are to:
- implement and extend profile microindentation techniques using micropipettes with customizable tips (spherical and needle-shaped) to measure viscoelastic properties and surface tension of diverse cell types,
- subject cell membranes to controlled compression and tension forces to quantify stress thresholds for rupture and transient pore formation,
- characterize rate-dependent rupture behavior and the specific role of the cytoskeleton in membrane me-chanical resistance,
- collaborate with computational mechanics groups to validate continuum models of membrane failure and optimize ultrasound treatment parameters.
We will address the following research questions:
- How do bulk viscoelastic properties and surface tension vary across cell types and physiological states, and what are their respective contributions to indentation force curves?
- What are the stress/tension/energy thresholds for membrane rupture under compression and tension, and how do they depend on loading rate?
- What is the specific contribution of the actin cortex and cytoskeleton to membrane rupture resistance, and can targeted cytoskeletal perturbations predictably shift rupture thresholds?
- Can a unified mechanical framework predict both viscoelastic deformation and membrane rupture from a common set of cell parameters, and translate to relevant ranges of ultrasound parameters?

Your Work Environment

The LadHyX laboratory hosts a dynamic research environment at Ecole polytechnique, with expertise in fluid me-chanics, soft matter, and biophysics. The PhD candidate will join an active group working on single-cell mechanics and benefit from strong local and national collaborative networks.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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